I want to register/transfer this domain to cloudflare but it is already expired. It keeps showing as unavailable in search when I try to add it as a new domain.
What steps have you taken to resolve the issue?
I have tried to transfer it instead of registering it and cannot do that either as it is already expired and the original registrar is not allowing me to update the DNS records.
You can’t register a domain simply because it’s expired: it has to go through the whole lifecycle (which can last over 2 months!) and be completely deleted from the registry before you can register it anew.
And you cannot transfer a domain to Cloudflare Registrar unless the domain is already active on Cloudflare (ie using Cloudflare nameservers). And since your registrar won’t let you change nameservers now, your only option is to first renew it at the current registrar.